Preforms are the products from which containers are made by blow molding. Unless otherwise indicated the term “container” is a broad term and is used in its ordinary sense and includes, without limitation, both the preform and bottle container therefrom. A number of plastic and other materials have been used for containers and many are quite suitable. Some products such as carbonated beverages and foodstuffs need a container, which is resistant to the transfer of gases such as carbon dioxide and oxygen. A resin now widely used in the container industry is polyethylene terephthalate (PET), by which term we include not only the homopolymer formed by the polycondensation of [beta]-hydroxyethyl terephthalate but also copolyesters containing minor amounts of units derived from other glycols or diacids, for example isophthalate copolymers.
Traditionally blow molding and filling have developed as two independent processes, in many cases operated by different companies. In order to make bottle filling more cost effective, some fillers have moved blow molding in house, in many cases integrating blow molders directly into their filling lines. The equipment manufacturers have recognized this advantage and are selling “integrated” systems that are designed to insure that the blow molder and the filler are fully synchronized. Despite the efforts in bringing the two processes closer together, blow molding and filling continue to be two independent, distinct processes. As a result, significant costs may be incurred while performing these two processes separately. Thus, efforts have been undertaken to develop a liquid or hydraulic blow molding system suitable for forming and filling a container in a single operation.
One process for simultaneously forming and filling a container is described in U.S. Pat. No. 8,573,964, hereby incorporated herein in its entirety by reference. During the process disclosed in the '964 patent a PET preform is heated prior to enter the blow molding system. The preform will exit an oven at about 140° C. During the molding process the temperature of the preform desirably stays between about 140° C. and about 63° C. (the phase change/solidification temperature of PET) to ensure resulting containers that are aesthetically and functionally desired. Accordingly, containers must be formed at or above the phase change/solidification temperature of the material used to form the container. The heated preform at its maximum temperature has a known (or knowable) amount of heat energy available to be distributed during formation of the container during the blow molding operation.
During the blow molding operation, heat energy is lost to the mold surrounding the preform, to the fluid used to expand the heated preform into the container, and heat energy is distributed along the larger surface area of the container formed from the stretched and blown preform. A portion of the heat energy of the preform is provided in the neck finish. The heat energy in the neck finish is unavailable for loss and/or distribution during the blow molding process because the neck finishes not being contacted by the fluid used for the blow molding operation nor disfigured or otherwise affected by the blow molding operation. Accordingly, a lesser portion of the total heat energy of the heated preform is available for distribution to the blow/fill fluid, mold, etc. Accordingly, undesirable heat losses may affect a consistency in the forming and filling of containers. It would be desirable to develop a preform and method of forming containers that maintains thermal properties of a heated preform during an expansion and filling thereof.